Heating apparatus for internal combustion engine exhaust aftertreatment

ABSTRACT

A heating apparatus for engine exhaust includes a housing having an inlet for connection in an exhaust gas conduit to receive exhaust gas and an outlet for connection in an exhaust gas conduit to discharge exhaust gas, the housing defining an interior space, a burner unit mounted in the housing for combustion of a fuel in the interior space, and, a turbocompressor, including a turbine having an inlet to receive exhaust gas to drive the turbine and an outlet connected to the housing to discharge exhaust gas and a compressor driven by the turbine and having an inlet to receive ambient air and an outlet connect to deliver compressed air to the burner. The turbocompressor may be mounted on the housing upstream of the burner unit.

FIELD OF THE INVENTION

The invention is directed to an apparatus for heating an exhaust flow from an internal combustion engine to make the exhaust temperature suitable for use by exhaust aftertreatment systems, for example, for regeneration of a diesel particulate filter, heating a diesel oxidation catalyst body, and/or heating a selective catalytic reduction catalyst body.

BACKGROUND AND SUMMARY OF THE INVENTION

Exhaust aftertreatment systems are used to remove certain substances from a combustion exhaust flow, as in the example of a particulate filter, and to convert some combustion products to other substances, as in selective catalytic conversion of oxides of nitrogen (NOx) into nitrogen gas and water.

For example, diesel particulate filters are used for removing particulate matter (typically the product of incomplete combustion) from the exhaust stream before releasing it to the environment. The collected particulate matter eventually loads the filter and must be removed. A currently-used approach is to raise the temperature of the filter to combust the collected particulate matter, a process called filter regeneration. This is done most conveniently by increasing the temperature of the engine exhaust gas. While in some engine applications, for example, over the highway trucks, the engine exhaust reaches temperatures sufficient to heat the particulate filter for regeneration, in other applications the work cycle does not produce sufficiently high exhaust temperatures and some intervention is required.

Various approaches are known, including temporarily changing the engine combustion parameters to raise the exhaust temperature and using heating device to add heat to the exhaust flow. Heating devices are typically a burner device that combusts a fuel and directs the combustion flow into the engine exhaust.

There are problems in current heating devices, including size (when the device is integrated with a diesel particulate filter), cost, and complexity of operation. The present invention is directed to a heating apparatus that solves problems in the art.

The invention proposes a heating apparatus that may be installed in a vehicle engine exhaust system as is convenient for that vehicle structure, the apparatus including an inlet to receive exhaust gas and an outlet to discharge exhaust gas, heated when the apparatus is operational, to the exhaust aftertreatment systems.

The apparatus according to the invention separates the heating apparatus from the diesel particulate filter, allowing for shorter diesel particulate filters and providing advantages for mounting the heating apparatus and DPF more conveniently.

The apparatus of the invention also provides a heating apparatus that separates the combustion control of the heating apparatus from the control of the engine, thus simplifying the controls of both systems and making diagnostics of problems simpler to resolve.

An apparatus according to the invention includes a housing defining an interior space and a burner mounted in the housing. The housing has an inlet and an outlet to connect the housing in an engine exhaust conduit. The inlet receives exhaust gas, and the outlet discharges exhaust gas. In the housing, exhaust gas is directed to flow around the burner, but exhaust gas does not make up part of the combustion air for the burner.

The apparatus further includes an air delivery device, preferably, a turbo-compressor that is driven by engine exhaust gas. An inlet to the turbine of the turbo-compressor is connected to the exhaust conduit and may be controlled by a valve. An outlet of the turbine connects to the exhaust conduit. The compressor of the turbo-compressor draws ambient air, compresses the air, and delivers compressed air to the inlet of the burner, having an outlet connected to the burner, An inlet of the compressor may be connected to a combustion air filter for the engine to draw filtered air, or have a dedicated air filter.

When the burner is active, the apparatus controls the valve to open so that exhaust gas drives the turbine and the compressor supplies combustion air to the burner. Engine exhaust gas flows into the housing around the burner, by which heat from the burner unit is carried off by the exhaust gas. The combustion gas from the burner and the exhaust gas combine in the housing and flow through the outlet of the housing, to a downstream portion of the exhaust conduit or directly into an exhaust gas aftertreatment device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the following Detailed Description read in conjunction with the appended drawings, in which:

FIG. 1 is a schematic of an exhaust gas heating apparatus in accordance with the invention shown in conjunction with an engine and exhaust aftertreatment system;

FIG. 2 is a front view of an embodiment of the invention;

FIG. 3 is a section view of the embodiment of FIG. 2, illustrating internal components and structure;

FIG. 4 is a side section view of a turbocompressor support unit of the invention;

FIG. 5 is a side section view of a burner support unit of the invention; and,

FIG. 6 is a side section view of an alternative embodiment of a burner support unit of the invention.

DETAILED DESCRIPTION

The invention will be described in conjunction with the appended figures. FIG. 1 is a schematic showing the apparatus 40 according to the invention, the components within the dotted line box, with an internal combustion engine 10 and exhaust gas aftertreatment systems 30, 32, and 34.

The engine 10 includes an intake manifold 12 for combustion air, and an exhaust manifold to discharge exhaust gas 14. The exhaust gas conduit 16 carries exhaust gas to a turbine 18 of a turbocharger. The turbine 18 is driven by the exhaust gas and is connected to drive a compressor 20. The compressor 20 compresses ambient air, which is delivered by a combustion air intake line 22 to the intake manifold 12. Ambient air is first filtered by a filter 24 to remove impurities, such as dust, from the air.

After exhaust gas exits the turbine 18, it is treated to remove pollutants and impurities by one or more aftertreatment systems. These may include a diesel oxidation catalyst 30, a particulate filter 32, and a selective catalytic reduction catalyst 34. These systems operate effectively within particular temperature ranges, and if the exhaust gas is not at a sufficiently high temperature, some heating is required. The apparatus 40 of the invention is advantageously suited to provide heat to the exhaust gas.

The heating apparatus 40 includes a housing 42 that encloses an interior space 44 that receives exhaust gas for heating. A burner 46 is mounted in the housing 42 and includes a combustion chamber 48 in which a fuel is combusted. The fuel may be provided by the engine's fuel system (not illustrated) for convenience. The housing 42 includes an inlet 50 to receive exhaust gas into the interior space 44 and an outlet 52 connected to discharge exhaust gas to the exhaust gas conduit 16.

A waste gas turbocompressor unit 60 provides compressed combustion air to the burner 46. The turbocompressor 60 includes a turbine 62 connected by a shaft 64 to drive a compressor 66. The turbine 62 is connected to receive exhaust gas through an inlet 70. The exhaust gas drives the turbine 62 and is discharged through turbine outlet 72 to the housing interior space 44. This may be by connection to the inlet 50 of the housing, as depicted in FIG. 1. Alternatively, the housing 42 may be extended to provide a mounting location for the turbocompressor 60, which would allow the turbine outlet 72 to be directly connected to the housing. According to another alternative, the housing inlet 50 may be configured as a large tubular structure to support the turbocompressor and provide for connection of the turbine with the housing interior space 44.

The turbine 62 is controlled by a valve 86 that controls a flow of exhaust gas to the turbine inlet 70. The valve may be disposed at an opening of the turbine inlet 70, as shown in FIG. 1. Alternatively, the valve may be disposed in the exhaust conduit between a junction with the turbine inlet 70 and the turbine outlet 72.

The compressor 66 draws ambient air through an intake 80, compresses the air, and delivers compressed air to a combustion air intake 49 of the burner 46. The ambient air is first drawn through a filter 24, which for convenience may be the same filter used for the engine combustion air, or may be a filter disposed at the compressor intake 80.

When the heating apparatus 40 is active, the burner 46 provides combustion gas to the interior space 44 that mixes with exhaust gas entering through the inlet 50. The exhaust gas flows over the burner 48, which results in some heat transfer from the burner to the exhaust gas, heating the exhaust gas and cooling the burner. The exhaust gas then mixes with combustion gas downstream of the burner, and the now higher temperature gas is discharged through the outlet 52.

The heating apparatus 40 includes a control unit to control the operation of the valve and the fuel injection and ignition of the burner 46. The control unit will be connected over the vehicle's data bus to receive signals from an engine electronic control unit, typically relating to a heat demand for regeneration of the DPF or warming of the SCR or DOC to operational temperatures, and electronic control units for the aftertreatment systems 30, 32, and 34, which may include the temperature reading for a system. The control unit will operate the heating apparatus responsive to the signals. A temperature sensor 54 is provided at the housing outlet 52 for monitoring the temperature of the exhaust gas discharged from the heating apparatus 40.

FIG. 2 shows a front view of an exemplary apparatus and FIG. 3 shows a side, section view of the exemplary apparatus with certain parts removed for clarity, as will be described.

The apparatus 110 includes a housing 112 that is configured to be disposed on an exhaust conduit of an internal combustion engine, as described above. The housing 112 includes an inlet 114 to receive exhaust gas and an outlet 116 to discharge exhaust gas. The housing 112 is formed by an outer wall 118 defining an interior space 120 for the flow therethrough of exhaust gas from the inlet 114 to the outlet 116.

A burner unit 130, which may be any known burner unit, is mounted in the housing 112 to provide combustion gas to the interior space 120. The burner unit 130 has an inlet 132 to receive a combustion air supply and a fitting 134 for a fuel line to supply an injector 136.

The burner 130 includes an ignition device (not illustrated) to ignite the fuel/air mixture introduced into the burner. The burner 130 includes a combustion chamber 140 disposed in the interior space 120 of the housing 112. A flow guiding cone 142 having a plurality of slots or other openings (not illustrated) is provided to guide the incoming compressed air in a swirl. In addition or alternatively, the combustion air inlet 132 may be oriented to produce the swirl flow in the combustion chamber 140. Preferably, the combustion chamber is a cylindrical wall mounted in the interior space 120, and spaced from the housing wall 118 to provide an annular space 144 (which is part of the housing interior space) surrounding the combustion chamber. According to an aspect of the invention, the wall 118 may be insulated.

The outer surface of the combustion chamber 140 includes one or more fins 146 extending into the annular space 144 to guide exhaust gas in a spiral flow pattern.

Downstream of the combustion chamber 140, the combustion gas from the combustion chamber and exhaust gas flowing through the interior space 120 mix in a mixing zone 148 and the mixture is discharged through the housing outlet 116. The mixing zone 148 may be a short or long as desired for the particular application of the heating unit.

The burner unit 110 is provided combustion air by a dedicated waste heat turbo-compressor (not illustrated for clarity) which is mounted on the housing 112 at a turbocompressor support location 160. The turbocompressor includes a turbine and a compressor, as known in the art. The turbine is connected to receive exhaust gas through an inlet gate 162 and returns exhaust gas to the housing through an outlet gate 164. A valve 170 in the housing 112 controls the flow of exhaust gas to the turbine to control turbine operation. The valve 170 is illustrated in FIG. 3 as a butterfly valve positioned between the inlet gate 162 and the outlet gate 164. In an open position, the valve allows the exhaust gas to flow through the interior space 120 without restriction. To have the turbine operational, the valve is pivoted to a position to divert a sufficient quantity of exhaust gas to drive the turbine and provide a pressure differential between the inlet gate 162 and outlet gate 164.

The turbine drives a compressor, as described in connection with FIG. 1, The compressor delivers compressed combustion air to the combustion air inlet 132, as previously described.

The arrangement of a heater with a dedicated combustion air source provides advantages. Conventional practice is to mix combustion air and engine exhaust gas into the burner unit, which can lead to fouling of the burner unit's components from the engine exhaust particulate matter and unburned fuel, which is avoided by the invention. In addition, control of combustion in the burner unit is improved through better control of the air/fuel mixture, the amount of combustible air in the engine exhaust not always being controllable or known with specificity.

A further advantage is that the combustion air is not being taken from the engine turbo-compressor, and thus control of engine combustion does not have to accommodate combustion in the burner unit. The engine does not have to adjust operation for the burner to function, and engine modes to generate higher exhaust gas temperatures can also be avoided.

The dedicated turbo unit, because of its limited duty, can be an inexpensive turbocharger device.

The heating apparatus may be constructed with a housing formed as a single unit as illustrated or with a turbocompressor unit and a burner unit. These parts may be directly connected, or connected on an exhaust conduit as convenient for the space available, the exhaust conduit geometry (angles and turns), or other factors.

FIG. 4 shows an exemplary turbocompressor unit 210 according to an alternative embodiment of the invention. The turbocompressor unit 210 is a tubular body having an inlet 214 and an outlet 216 and includes a mounting location 260 for a turbocompressor. The inlet and outlet may connect the turbocompressor unit 210 in an exhaust conduit

FIG. 5 is an exemplary burner unit 310. The burner unit includes a housing 312 and burner as described above, and has an inlet 314 and an outlet 316 for connecting the unit in an exhaust conduit.

FIG. 6 is an alternative embodiment of a burner unit 410. The burner unit 410 has an inlet 414 and an outlet 416 arranged perpendicular to the longitudinal axis of the housing 412.

The invention has been described in terms of preferred principles, embodiments, and components. Those skilled in the art will understand that substitutions of equivalent structures, components and method steps may be done without departing from the scope of the invention as described. 

What is claimed is:
 1. A heating apparatus for an engine exhaust, comprising: a housing having an inlet for connection in an exhaust gas conduit to receive exhaust gas and an outlet for connection in an exhaust gas conduit to discharge exhaust gas, the housing defining an interior space; a burner unit mounted in the housing for combustion of a fuel in the interior space; and, a turbo-compressor, including a turbine having an inlet to receive exhaust gas to drive the turbine and an outlet connected to the housing to discharge exhaust gas and a compressor driven by the turbine and having an inlet to receive ambient air and an outlet connect to deliver compressed air to the burner.
 2. The heating apparatus of claim 1, wherein the burner unit comprises a combustion chamber disposed in the interior space, including a wall enclosing a combustion space, the wall being spaced from the housing to provide an exhaust flow space surrounding the combustion chamber.
 3. The heating apparatus of claim 2, wherein the housing wall is insulated.
 4. The heating apparatus of claim 2, wherein the housing inlet communicates with the exhaust flow space to direct exhaust gas into the exhaust flow space.
 5. The heating apparatus of claim 2, wherein the combustion chamber wall includes fins formed on an outer surface extending into the exhaust flow space and oriented to guide exhaust gas in a spiral flow.
 6. The heating apparatus of claim 1, comprising a valve to control a flow of exhaust gas to the turbine inlet.
 7. The heating apparatus of claim 1, wherein the housing inlet comprises an extended tubular member, wherein the turbo-compressor is mounted to the tubular member with the turbine inlet and turbine outlet connected to the tubular member.
 8. The heating apparatus of claim 1, wherein the burner includes a combustion air inlet connected to receive air from the compressor outlet, the combustion air inlet oriented to guide an inflow of combustion air in a swirl pattern in the burner.
 9. The heating apparatus of claim 1, wherein the housing includes a mixing space allowing combustion gas from the burner and exhaust gas to mix before being discharged through the housing outlet. 